This section is intended to provide a background or context to the invention that is, inter alia, recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The need for accurate radiation surveillance is expanding as the perceived risk of unsecured nuclear materials entering and transmitting within the country increases. Tracking systems are required to detect, locate, and track a radiation source. Such a system is described in U.S. Pat. No. 7,465,924. After increased publicity of terrorist attacks there has been a fear that terrorists would carry a nuclear weapon or material into the US and cause catastrophic damage. One area of investigation has been on gamma radiation detection systems for shipping containers or trucks. This is a formidable task given the number of shipping containers, with the added consideration that the nuclear material/device may be in a shielded location. Some solutions have been developed; however, the detection equipment is not lightweight, nor easily portable, detection times are slow, and require essentially a stationary target. The concern is that a terrorist would carry a radioactive source and detonate it at a public event, such as a football game. Because a source would have to be carried to such an event, sensors placed outside the event or in a nearby subway/transit system could also provide an earlier detection method. In a crowded area, spectators provide shielding for the radioactive material in a nuclear device and make source detection difficult.
Current systems for detecting and tracking radioactive sources include a live video image of an area that includes the detected radioactive source. Further, current systems determine the most likely location of a radiation source. However, current systems lack the ability of determining the amount of shielding between the radiation source and a radiation detector. Current systems either make assumptions regarding the amount of shielding or ignore the impact of shielding.
Thus, there is a need for a source tracking system and methods for same which 1) determine the amount of shielding, 2) allow determination to be made in real-time, 3) allow for determination of the amount of shielding in a dynamic environment, and 4) rely on the spectral data from the source tracking system without the need for additional specialized detection equipment so that the source tracking system can more accurately predict the location of the source. These capabilities need to be provided in a way that maximizes the amount of data that the system can process.